Electrically operated steam heater

ABSTRACT

An electrical heater for heating steam to a superheated temperature has a longitudinal heating element disposed within a glass or ceramic tube which, in turn, is disposed within a metal cylinder. The heating element is made of resistance wire and has a cyclical spiral shape for efficient heat transfer. Steam is introduced into one end of the metal cylinder, passes through the heater and exits from the other end as superheated steam.

United States Patent [191 Edin [ Jan. 1,1974

[ ELECTRICALLY OPERATED STEAM HEATER [75] Inventor: Ronald E. Edin,Straham, NH.

[73] Assignee: GTE Sylvania Incorporated,

Danvers, Mass.

[22] Filed: Mar. 2, 1973 [21] Appl. No.: 337,594

[52] U.S. Cl 219/381, 219/374, 219/375,

219/401, 219/546, 219/553, 338/298, 338/302 [51] Int. Cl. H05b 3/02 [58]Field of Search 219/364, 368, 370,

3,094,606 6/1963 Ferris 219/375 X 3,109,912 11/1963 Cerulli 219/3813,212,486 10/1965 Lorge 219/374 X 3,356,830 12/1967 Schleer et al.219/373 3,551,643 12/1970 Pricenski 219/381 3,560,710 2/1971 Fuellemann219/373 3,598,538 8/1971 Peacock 219/381 X 3,654,431 4/1972 Brooks et al219/381 X Primary Examiner-Velodymyr Y. Mayewsky Att0rney-Norman J.OMalley et a1.

[5 7 ABSTRACT An electrical heater for heating steam to a superheatedtemperature has a longitudinal heating element disposed within a glassor ceramic tube which, in turn, is disposed within a metal cylinder. Theheating ele- 23/281, 288,8 ment is made of resistance wire and has acyclical spiral shape for efficient heat transfer. Steam is intro- [56]References Cited duced into one end of the metal cylinder, passes UNITEDSTATES PATENTS through the heater and exits from the other end as su-1,17|,0s9 2/1916 Loguin 338/296 x perheated steam 2,957,154 10/1960Strokes 338/299 3 Claims, 1 Drawing Figure s lo 8 7 4 l #L I PATENTEDJAN1 I974 N n m Ii) =lilllllulllilll-iurlrnlrlrrrllrvl ELECTRICALLYOPERATED STEAM HEATER THE INVENTION Electrically heated steam heaters ofthe prior art have generally been quite bulky and have used inefficientsheathed heating elements, which prevented direct contact between theheating element and the steam.

This invention concerns a small inexpensive steam heater in which thesteam passes directly through the turns of the heating element forefficient heat transfer.

The single FIGURE in the drawing is an elevational view, partly insection, of a steam heater in accordance with this invention.

Metal cylinder 1 is a container for heating element 2 and is the conduitthrough which the steam to be heated flows. In one example, metalcylinder l-was a inch length of half-inch stainless steel pipe, threadedat the inlet end, to permit connection to a source of steam. The outletend could also be threaded to permit connection to apparatus utilizingthe superheated steam.

Heating element 2 is a longitudinal cyclical spiral corrosion resistantwire wound element having the construction shown in US. Pat. Nos.3,551,643 and 3,598,538 in order to cause turbulence in the flow ofsteam therethrough. In the above example, heating element 2 consisted of125 turns of 28.5 mil kanthal wire, and had an outer diameter of 0.477inch, an inner diameter of 0.212 inch, a total wire length of 12.1 feet,a heater body length of 6 inches and a cold resistance of 125 ohms.

Disposed around heating element 2 is quartz glass tube 3 whichelectrically insulates heating element 2 from metal cylinder 1. Heatingelement 2 is a slip fit into tube 3, but can have sufiicient frictionalengagement of the wire turns of heating element 2 with the inner wall ofquartz tube 3 so that heating element 2 is not easily slidable withinquartz tube 3. Tube 3, in turn, is a slip fit into metal cylinder 1.Tube 3 extends beyond both ends of heating element 2 to prevent physicalcontact of element 2 with cylinder 1.

Quartz tube 3 is longitudinally positioned within cylinder 1 by means ofmetal tubular spacer 4 which is attached, such as by welding, tocylinder 1 at the exit end thereof. Spacer 4 has about the same diameteras tube 3 and tube 3 abuts thereagainst within cylinder 1. The other endof tube 3 may abut against a similar metal tubular spacer to preventaxial movement of tube 3 within cylinder 1 or may abut against feedthrough insert 6. Instead of tubular spacers, other means may be used tolongitudinally hold tube 3 within cylinder 1, such as pins or screwsprotruding through the wall of cylinder 1.

Near the inlet end of cylinder 1 are electrical connectors which providefor connection of the heater to an external source of electrical power.In the above example, the electrical connectors consisted of two ceramicand metal feed through connectors 5 fastened orthogonally to metalcylinder 1 and opposite each other. Extending through and fastened toconnectors 5 are metal feed through inserts 6 to which heating element 2is connected. Feed through inserts .6 extend slightly into the bore ofcylinder 1 to act as a stop for tube 3.

Heater element 2 was mounted on threaded ceramic rod 7 which had anaxial hole therethrough. The grooves of ceramic rod 7 engaged only partof each turn of heating element 2, because of the polygonal shape of theturns, but there was sufficient engagement therebetween to maintainuniform space between turns throughout the life of the heater. Ceramicrod 7 was 6 inches long, had 20 threads per inch, an outer diameter of250 mils, a root diameter of 200 mils and a mil axial hole therethrough.

The innermost end of heating element 2 was directly connected to one ofthe feed through inserts 6 by inserting leg 8 of element 2 directly intoan axial hole in said insert and fastening it with a small screw (notshown). The other end of heating element 2 was connected to the other ofsaid feed through inserts by means of center lead wire 9 which extendedcompletely through the axial hole of ceramic rod 7. To provide a secureconnection that lasts throughout the useful life of the heater, end 10of heating element 2 and the end of center lead wire 9 were insertedinto a small metal coil 11 and welded together.

At 1 10 volt operation, the heater drew 8 amperes of current and heated212F stem to a superheated temperature of 600F at a rate of standardcubic feet per hour.

I claim:

1. An electrically operated steam heater comprising: an elongated metalcylinder open at both ends; a longitudinal cyclical spiral corrosionresistant wire wound heating element, having an axial bore therethrough,disposed in said cylinder, the individual turns of said heating elementbeing substantially polygonal in shape; a ceramic tube positioned withinand attached to said metal cylinder encircling said heating element andelectrically insulating said heating element from said metal cylinder; aceramic rod having an axial hole therethrough disposed within the boreof said heating element said ceramic rod being externally threaded andsaid heating element being threaded onto said ceramic rod; twoelectrical connecting means attached to said metal cylinder forconnecting said heater to an external source of electrical power, theend of said heating element that is more distant from said electricalconnecting means being connected to one of said electrical connectingmeans by a wire passing through the axial hole of said ceramic rod, theother end of said heating element being directly connected to the otherelectrical connecting means each of said electrical connecting meanscomprising a ceramic and metal feed through and a metal feed throughinsert; two means to longitudinally position said glass tube in saidmetal cylinder, said feed through inserts are one of the means forlongitudinally positioning said glass tube in said metal cylinder; andmeans to connect said heater to a source of steam.

2. The heater of claim 1 wherein another means for longitudinallypositioning said glass tube in said metal cylinder is a tubular metalspacer welded to said metal cylinder.

3. The heater of claim 1 wherein said further end of said heatingelement and said wire passing through said ceramic rod both extend intoa small metal coil where they are welded together.

1. An electrically operated steam heater comprising: an elongated metalcylinder open at both ends; a longitudinal cyclical spiral corrosionresistant wire wound heating element, having an axial bore therethrough,disposed in said cylinder, the individual turns of said heating elementbeing substantially polygonal in shape; a ceramic tube positioned withinand attached to said metal cylinder encircling said heating element andelectrically insulating said heating element from said metal cylinder; aceramic rod having an axial hole therethrough disposed within the boreof said heating element said ceramic rod being externally threaded andsaid heating element being threaded onto said ceramic rod; twoelectrical connecting means attached to said metal cylinder forconnecting said heater to an external source of electrical power, theend of said heating element that is more distant from said electricalconnecting means being connected to one of said electrical connectingmeans by a wire passing through the axial hole of said ceramic rod, theother end of said heating element being directly connected to the otherelectrical connecting means each of said electrical connecting meanscomprising a ceramic and metal feed through and a metal feed throughinsert; two means to longitudinally position said glass tube in saidmetal cylinder, said feed through inserts are one of the means forlongitudinally positioning said glass tube in said metal cylinder; andmeans to connect said heater to a source of steam.
 2. The heater ofclaim 1 wherein another means for longitudinally positioning said glasstube in said metal cylinder is a tubular metal spacer welded to saidmetal cylinder.
 3. The heater of claim 1 wherein said further end ofsaid heating element and said wire passing through said ceramic rod bothextend into a small metal coil where they are welded together.